I have just installed a car radio in my Skoda Fabia and now the central locking sensor doesn't work - the central locking still works on the key. Also the warning signal when opening the door with the lights on is not working. It doesn't appear to be a fuse problem. any ideas?

My mate had this problem with his polo. in the end up he put his factory standard CD player back in. If anyone has the answer to this it would be great to know why it happens.